The present invention relates to a terminal structure and a process of fabricating it. In one aspect of the present invention, it relates to a process of fabricating a hybrid-IC device having a multiplicity of input and output terminals, and a terminal structure thereof.
In another aspect of the invention, it relates to a mounting structure for input and output terminals of modules such as IC, LSI, etc., and more particularly to a mounting structure for one-surface terminals.
A prior-art hybrid IC device of the type having a multiplicity of input and output terminals is soldered to a substrate by reflow of the components and the input and output terminals are also soldered onto the substrate. As shown in FIG. 1, one end of each lead 71 is bent to have an inverted U-shaped 73, and the tip 72 of the lead 71 is made to abut a soldering pad 75 substantially at right angles to permit soldering by reflow (Japanese Utility Model Application Kokai Publication No. 43,452/1988).
In another method shown in FIG. 2 in which input and output terminals are formed on one surface of the substrate, a lead frame 81 is formed substantially in a hat shape, a notch 84 is provided in part of the hat to clamp the substrate, soldering is performed by dipping, and the connecting part 83, is later removed to form lead terminals (Japanese Patent Application Kokai Publication No. 266,856/1987).
When the number of input and output terminals required in a hybrid IC device is large, it is not possible to connect all of them on one surface of the substrate, and it is necessary to connect them on both surfaces of the substrate. Moreover, the throughhole pitch of the mother board on which a hybrid IC device is mounted is standardized and is usually 2.54 mm for the reason of strength, easy manipulation, etc. To obtain connection of input and output terminals in a limited length of mounting, it is necessary to arrange them in a plurality of rows. However, with the prior-art terminal structures, it is different to fix, by reflow or soldering-dip, a multiplicity of terminals on both surfaces of the substrate.
Other problems of the prior art will now be described with reference to FIG. 3 to FIG. 7. The input and output terminals of modules such as IC's, LSI's, etc. (hereinafter simply referred to as modules) have such a structure shown in FIG. 3 to FIG. 7, and are connected to the substrate in the module.
FIG. 3 shows an example in which clip terminals are used. The substrate 101 of the module has a surface on which electronic components, devices, etc., not shown, are mounted, and these components, devices etc. are electrically connected by means of a wiring pattern, not shown. The wiring pattern has terminal pads 102a for connection with the input and output terminals at an end of the substrate 101. When the substrate 101 is inserted in the clip terminal 109, the clip terminal 109 clamps the substrate 101 by virtue of its resiliency. The clip terminal 109 and the substrate 101 are fixed provisionally. In this state, the clip terminal 109 and the terminal pads 102a are electrically connected by solder 103a, so good values are obtained with regard to the reliability of the connection resistance and the pull strength. Moreover, in recent years, a greater demand has existed for a higher density of mounting of electronic components. To meet this demand, wiring patterns 106a and 106b are provided as shown in FIG. 4, or additional terminal pads 102b are provided on the reverse surfaces of the substrate 101 as shown in FIG. 5. In these cases, the clip terminals shown in FIG. 3 cannot be used, so one-surface terminals 104c and 104e in abutment with one surface of the substrate 101 are used and fixed to terminal pads 102a with solder 103a.
With the structure shown in FIG. 3, the substrate is clamped on both surfaces, so wiring patterns and terminal pads cannot be disposed on the reverse surface of the substrate, and therefore the input and output terminals cannot be provided on both surfaces of the substrate. With the structure shown in FIG. 6 and FIG. 7, the terminals are in contact with only a single surface of the substrate, so there is a problem that the reliablity of the connection resistance and the pull strength is low compared with the clip terminals shown in FIG. 3. Moreover, because the terminals are on one surface and the substrate are fixed by solder alone, a large quantity of solder is required and the areas for the terminal pads are substantial.